Stoker



Jan. 1, 1946. w.v A. RIDDEYLI.

STOKER Filed July 19, 1944 2 Sheets-Sheet l me/rm L L l. D m

A. M M L H.

Jan. l, 1946.

W. A. RIDDE LL.

STOKER Filed July 19, 1944 UJiLuAM A. Rmneu.

2 sheets-shed 2 Patented Jan. l, 1946 STOKER william A. maden, Frederick, Md., signor u The General Engineering Company, Frederick,

Md., a corporation of Maryland Application July 19, 1944, Serial No. 545,587

(Cl. 11G-45) 2 Claims.

This invention relates to coal stokers, particularly of the industrial type, for burning bituminous coal, and the main object is to provide mechanism of a novel, efilcient and practical nature for pre-oxidizing the fuel before it enters the burner,

so as to prevent or at least greatly retard coking and thereby improve combustion and provide greater general efficiency of the stoker, with resulting economy in fuel consumption.

In its broader aspects the invention is shown and described in my copending patent application Serial No. 538,790 filed June 5, 1944, for Stoker and method for pre-oxidizing coal. In the present instance, however, the invention embodies certain novel features of construction not disclosed in the earlier filed application.

ln the accompanying drawings which illustrate a preferred embodiment of the present invention- Fig. 1 is a longitudinal sectional elevation of a coal Stoker embodying the invention.

Fig. 2 is a plan view of the apparatus as shown in Fig, l, but with the coal hopper shown in section, as on line 2--2 in Fig. l.

Fig. 3 is an enlarged detail section, as on line 3--3 in Fig. l, showing the arrangement for admitting air into the hollow auger shaft which feeds the coal from the hopper to the burner.

Fig. 4 is an enlarged detail section, on line Il--II in Fig. 1, and through one of the air vents through which the pre-oxidizing air is discharged from the feed auger into the conveyed coal.,

Figs. 5, 6, and 7 are sectional elevations showing modified forms of feed screw units as may be used in slightly different types of stokers.

Referring to the drawings more particularly and by reference characters A designates the hopper of a stoker from which hopper coal is conveyed by an auger or screw B through a tube C to the burner or retort unit D. The auger Bis rotated by a shaft 5 (Fig. 3) that is fixed in one end thereof and extends from a transmission unit 6 which also operates a centrifugal fan E, the unit B being driven by a motor F. The fan E supplies air under pressure, through a duct G, to the burner D in well known manner.

The feed screw or auger B is formed in part by a hollow shaft 'I about which is disposed the spiral vane or flights 8 which extend substantially the entire length of the shaft. Air under pressure from the fan E is supplied to the interior of the shaft I1, through any suitable connection, but in the present instance, and for purpose of illustration, I haveshown the hopper end of the shaft (Fig. 3) as provided with apertures or ports 9' which open into the annular inner chamber I0 of a collar Il. This collar has flanges I2 engaged in sealing rings I3 fixed on the shaft 1, so that the shaft may rotate within the collar which remains stationary. A pipe I5 connects the collar II to the air duct G, and thus not only provides air to the shaft 1 but prevents rotation of the collar II therewith.

The air forced into pipe 1 is discharged therefrom, and into the coal conveyed by the auger B, through ports I5 formed by cam shaped lugs or y projections I6. These lugs are disposed between flights of the auger over a portion of the length thereof nearest the burner, and it will be noted that the lugs and ports are so formed that the air will be discharged in a rotational direction opposite to the rotational movement of the auger. This arrangement not only prevents coal from clogging the ports but also insures full and proper saturation of the coal by the air before it reaches the burner. It will be understood that since there are no port lugs such as I5 on the section of the auger nearest the hopper the coal will be conveyed through the first half portion of the tube C in fairly closeor compact mass form, with a result that it effectively stops the escape of air and gases rearwardly into the hopper from which it could escape to the furnace room. This condition does not obtain in the second section as there the lugs IG have a tendency to break up the coal mass which is desirable since it can then better become air charged.

In the modification shown in Fig. 5 it will be seen that the auger BI has its spiral vane I'I formed substantially as in Fig. 1 up to the point Iii, but from there on the flights I 9 are more widely spaced with a result that the coal conveyed through the terminal end of the tube C is moved faster but is thereby expanded or loosened up, leaving voids with a result that the air coming in through the lugs I6 will more readily mix with the coal. l

The form shown in Fig. 6 is for a more elongated type of retort, and in this case the air discharge lugs are all located beyond the terminus of pipe C. In this case, too, the flights 20 of the spiral conveyor are stretched or .spaced as in Fig. 5, but do not extend to the end of the pipe 2l, a considerable end portion of which is provided only with the air opening lugs I6.

In Fig. 7 the spiral vane extends to the end of the air pipe 22, but the widely spaced flights 23 extend considerably back into the coal tube, as does the series of air discharge ports IB.

It is understood that suitable modiiicatiom and variations in the invention, as above set forth. may be made without departing from the spirit and scope o'f the appended claims. Having now therefore fully illustrated and described my improved apparatus and the method oi' practicing the same, what I claim to be new and desire to protect by Letters Patent is:

l. InV a stoker, a coal tube, a rotatable auger within the tube, said auger having a hollow shaft, means for introducing air into said shaft, and lugs' formed on the shaft and having ports through which air may escape from the shaft in a rotational direction opposite to the rotation of the shaft into the coal conveyed by the auger, said lugs having outer cam acting surfaces.

2. In a Stoker, a coal tube for supplying coal to the stoker, a power operated rotatable auger in the tube for advancing the coal therethrough. said auger having a hollow shaft for the passage of air, lugs extending integrally from the shaft, between auger flights, and having cam acting outer surfaces for engaging the coal as it is being advanced through the tube by the auger, and said lugs having ports through which air may escape from the shaft into the conveyed coal and in a direction opposite to the rotation of the auger.

v WILLIAM A. RIDDELL. 

